package com.tyrone.concurrent.lock;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

/**
 * @author xieyl
 * @create 2021/12/9 21:48
 */
public class TwinsLock implements Lock {
    
    private  final  Sync sync = new Sync(2);
    
    private static final class Sync extends AbstractQueuedSynchronizer{
        
        Sync(int count){
            if (count<0){
                throw new IllegalArgumentException("count must large than zero");
            }
            setState(count);
        }
        
        @Override
        protected int tryAcquireShared(int reduceCount) {
            for (;;){
                int current = getState();
                int newCount = current - reduceCount;
                if (newCount < 0 || compareAndSetState(current,newCount)){
                    return newCount;
                }
            }
        }

        @Override
        protected boolean tryReleaseShared(int addCount) {
            for (;;){
                int current = getState();
                int newCount = current + addCount;
                if (compareAndSetState(current,newCount)){
                    return true;
                }
            }
        }
    }
    
    @Override
    public void lock() {
        sync.acquireShared(1);
    }

    @Override
    public void lockInterruptibly() throws InterruptedException {
        
    }

    @Override
    public boolean tryLock() {
        return false;
    }

    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
        return false;
    }

    @Override
    public void unlock() {
        sync.releaseShared(1);
    }

    @Override
    public Condition newCondition() {
        return null;
    }
}
